The present trend to farms, ranches and fruit groves of everincreasing acreage is the result of the need to reduce unit costs of production. As a result, implements such as fertilizer and insecticide spreaders and sprayers, plows, cultivators, harvesters pickers and many other kinds and types are made of constantly-increasing sizes and capacities. Likewise the tractors required to power the larger and heavier implements, must be correspondingly increased in size and power. Whereas the small tractors of earlier years were relatively inexpensive, those used to-day are so costly that it is necessary as a matter of simple economics, to utilize them as nearly continuously as possible, in order to pay interest on their purchase price and amortize the investment. This is also true of the implements themselves although, of course, many of these, such as plows and harvesters can only be used seasonally or occasionally. But such costly implements can only be economically justified by keeping them working as many days as possible throughout the year. This means greater acreage per implement.
The foregoing considerations call for a hitch by which heavy-duty tractors may be readily coupled to and uncoupled from a multiplicity of implements of large capacities. A tractor-implement combination is only as useful as the hitch by which the two are coupled; and so that hitch must be capable of pulling the heaviest and largest of a great assortment of agricultural implements available to-day. It is therefore necessary that modern hitches be extremely strong in proportion to their weight, and pulling power, relatively simple to fabricate and repair, and, most importantly, just about 100% reliable in operation. Even one breakage of a hitch at use in the field can result in the loss of several hundreds of dollars in wages and down time of the machines.
Prior art hitches are either too weak to cover the higher ranges of pull encountered to-day, or they are unduly complicated and expensive to build, service and repair. Many of them embody specially-shaped parts requiring costly forging, stamping, pressing or machining. Even more important, many prior art hitches, due to their complicated construction and multiplicity of parts, are difficult to engineer correctly. For instance it is obviously a desideratum of a well-engineered hitch, that the pull from tractor to implement pass through the hitch as simply and directly as possible, without numerous interchanges between shear, tension and bending moments. For each such interchange requires an engineering computation taking into consideration a factor of safety, and allowable strength of the metal in shear, tension and bending. The result is that often one part will be made too light or weak and thus fail in service, while another will be overly strong and heavy.